1. Field of the Invention
The present invention relates to input devices, and in particular, to a ratchet structure for use in an input device such as a computer mouse.
2. Description of the Prior Art
The increased popularity of personal computers (PCs) also means that the accompanying input devices, such as computer mice, are widely used as well. Many computer mice are provided with a roller thereon for controlling the movement of a Z-axle on the display. This Z-axis control mechanism is often used for scrolling a screen and is especially useful in Internet applications. Examples include U.S. Pat. No. 6,198,057 for a rotary operating-type electronic device, U.S. Pat. No. 6,157,369 for an optical-mechanical roller with ratchet, U.S. Pat. No. 6,326,949 for a wheel support guide for vertical wheel support movement, and U.S. Pat. No. 5,912,611 for a Z-encoder mechanism.
The above-mentioned patents disclose complicated Z-axis devices positioned at the base of the input device for supporting a wheel or roller support mechanism. The roller can be pressed to activate a micro switch for controlling certain operations. Some of these Z-axis devices also provide a corresponding ratchet mechanism that provides a ratchet feedback effect while the roller is being turned by a user. The turning of the roller with a ratchet mechanism also allows for precise positioning at the desired location.
Although the above-mentioned patents describe Z-axis devices that can achieve the effect of precise control when turning the roller, a number of drawbacks still remain. For example, the Z-axis devices in U.S. Pat. Nos. 6,157,369 and 6,326,949 occupy smaller operating spaces, but each involves a complex structure that carries with it a higher cost to produce. The large variety of the components in each of these structures will result in a higher molding cost, and will also make them hard to assemble, especially when the manufacturing will require an increased number of operating procedures with small tolerances for error.
As another example, U.S. Pat. No. 5,912,611 discloses a Z-axis device that has a simple structure but the structure occupies a larger space, which goes against the modern trend of minimizing the sizes of all electronic products.
Thus, there still remains a need for a Z-axis device that has a simple structure which occupies minimal space and which is inexpensive to manufacture.